This comment illustrates one of the more challenging aspects of determining the efficacy and safety of the diverse probiotic products available to patients. Efficacy is based on well-done, randomized clinical trials using specific probiotic formulations and strains. Strain designations and brand names may change over time, requiring careful tracing of probiotic strains over time. Also, a probiotic product claiming efficacy may be produced by different manufacturers who claim their product is backed by research their company did not conduct. The issue with this is different manufacturing processes may effect the biological properties of a probiotic, which may impact it’s true efficacy.1 Indeed, quality control studies of probiotic products on the market may show differences in quality and efficacy, even for products claiming to contain the same strain or strains.1 We reviewed the most recent strain designations and brand names in our recent guide, often confirming the product identification using manufacturer’s websites.2 As this is a shifting target at best, we presented what we found in good faith. One of the probiotics listed in our guide listed 8 strains in a product called VSL#3. We had verified these strain designations on VSL#3’s current website. Consequently, De Simone published a letter indicating that there is currently a new formulation of VSL#3 by an Italian manufacturer which uses different manufacturing processes and only contains 7 strains.3 A study compared the original VSL#3 formulation (“De Simone Formulation”) manufactured in the USA to the newer VSL#3 product manufacturer in Italy and found differences in biological properties between the two formulations.4 The newer VSL#3 formulation is not supported by any independent clinical trials. As a consequence, we would like to correct the designations of the VSL#3 product listed in our guide from the strain designations given in the text and Table 1 to: “8 strain mixture: Bifido. breve DSM24732, Bifido. longum DSM24736, Bifido. infantis DSM24737, L. acidophilus DSM24735, L. plantarum DSM24730, L. paracasei DSM24733, L. delbruckii subsp. bulgaricus DSM24734, Strept. thermophiles DSM24731, originally named VSL#3®, now either Visbiome™ or Vivomixx™ using the De Simone formulation.


1. McFarland LV. From Yaks to Yogurt: The history, development and current use of probiotics. Clin Infect Dis 2015; 60(S2):S85-S90. doi: 10.1093/cid/civ054, PMID: 25922406
2. Sniffen JC, McFarland LV, Evans CT, Goldstein EJC. Choosing an appropriate probiotic product for your patient: An evidence-based practical guide. PLOS One 2018 Dec 26;13(12):e0209205. doi: 10.1371/journal.pone.0209205
3. De Simone C. Letter: what gastroenterologists should know about VSL#3. Aliment Pharmacol Ther 2018 Mar;47(5):698-699. doi: 10.1111/apt.14515.
4. Trinchieri V, Laghi L, Vitali B, et al. Efficacy and safety of a multistrain probiotic formulation depends from manufacturing. Front Immunol 2017;8:1474.